Thermophysical characteristics of the formed layer of foam coke when protecting fabric from fire by a formulation based on modified phosphorus-ammonium compounds

This paper reports the analysis of flame retardants for fabrics that has established that the meagerness of the data that explain and describe the process of fire protection, as well as the neglect of elastic coatings, leads to the combustion of structures made from fabrics under the influence of flame. The development of reliable methods to study the fire protection conditions for fabrics leads to the design of new types of fireproof materials. Therefore, it becomes necessary to define the conditions for the formation of a barrier for burning and flame propagation by a piece of fabric and for establishing a mechanism that would inhibit a temperature transfer to the material. To address this issue, an estimation-experimental method has been devised for determining thermal conductivity when using a fire protection agent as a coating, which makes it possible to assess the thermal conductivity coefficient under the effect of high temperature. Based on the experimental data and theoretical dependences, the coefficient of thermal conductivity for the fire-resistant layer of foam coke was calculated, 0.034 W/(m∙K), which, accordingly, ensures the heat resistance of the fabric. The study results have proven that the process of the thermal insulation of fabric involves the formation of soot-like products at the surface of the sample. The inhibition of the process of heat transfer to the material treated with a composition based on modified phosphorus-ammonium compounds is characterized by the formation of a heat-protective layer of coke at the surface of the fabric. The maximum possible penetration of temperature through the thickness of the coating has been estimated. At the surface of the sample, a temperature was generated that significantly exceeds the ignition temperature of the fabric, and, at the non-heated surface, does not exceed 150 °C. Thus, there is reason to assert the possibility of targeted adjustment of fire protection processes in the fabric by applying coatings that can form a protective layer on the surface of the material, which inhibits the rate of heat transfer

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Establishing patterns of mass transfer under the action of water on the hydrophobic coating of the fire-retardant element of a tent

Eastern-European Journal of Enterprise Technologies ◽

10.15587/1729-4061.2021.237884 ◽

2021 ◽

Vol 4 (10(112)) ◽

pp. 45-51

Author(s):

Yuriy Tsapko ◽

Zinovii Sirko ◽

Roman Vasylyshyn ◽

Oleksandr Melnyk ◽

Аleksii Tsapko ◽

...

Keyword(s):

Mass Transfer ◽

Fire Protection ◽

Flame Retardants ◽

Fire Retardant ◽

Protective Layer ◽

Water Repellent ◽

Water Penetration ◽

Hydrophobic Coating ◽

Study Results ◽

Fabric Surface

This paper reports an analysis of the flame retardants for fabrics that has revealed the fact that the meagerness of data to explain and describe the process of fire protection, specifically the neglect of elastic coatings, leads to that the structures made from fabrics are ignited under the influence of a flame. Devising reliable methods to study the fire protection conditions for fabrics results in the design of new types of fireproof materials. Therefore, there is a need to determine the conditions for the formation of a barrier for water mass transport and to establish a mechanism for slowing down water penetration through the material. In this regard, an estimation-experimental method has been constructed for determining mass transfer under the action of water when using a hydrophobic coating, which makes it possible to assess water penetration. Based on the experimental data and theoretical dependences, the intensity of mass flow under the action of water has been determined, which is 0.000177 kg/m2, which ensures fabric resistance. The study results have proven that the process of waterproofing the fabric involves inhibition of the mass transfer process under the action of water by insulating the surface of the fireproof fabric with a hydrophobic coating. It should be noted that the presence of a hydrophobic coating leads to blocking the fabric surface from moisture penetration. Such a mechanism behind the effect of the hydrophobic coating is likely the factor in adjusting the process through which the integrity of an object is preserved. Thus, the sample of fireproof fabric coated with a water repellent demonstrated, after exposure to water, that the amount of water absorbed did not exceed 0.00012 kg, and, for a fabric without a water repellent, was 0.01 kg. Thus, there is reason to assert the possibility of targeted adjustment of the processes related to water penetration of the fabric by using hydrophobic coatings that could form a protective layer on the surface of the material, which inhibits the rate of water penetration.

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Characteristics of supercritical heat transfer during filmboiling of nanofluids on a vertical heated wall

Nuclear and Radiation Safety ◽

10.32918/nrs.2018.4(80).05 ◽

2018 ◽

pp. 29-35

Author(s):

А. Avramenko ◽

M. Kovetskaya ◽

A. Tyrinov ◽

Yu. Kovetska

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Mathematical Model ◽

Mass Transfer ◽

Heat Flux ◽

High Temperature ◽

Heat And Mass Transfer ◽

Heated Surface ◽

Heated Wall ◽

Film Boiling

Nanofluid using for intensification of heat transfer during boiling are analyzed. The using boiling nanofluids for cooling high-temperature surfaces allows significantly intensify heat transfer process by increasing the heat transfer coefficient of a nanofluid in comparison with a pure liquid. The properties of nanoparticles, their concentration in the liquid, the underheating of the liquid to the saturation temperature have significant effect on the rate of heat transfer during boiling of the nanofluid. Increasing critical heat flux during boiling of nanofluids is associated with the formation of deposition layer of nanoparticles on heated surface, which contributes changing in the microcharacteristics of heat exchange surface. An increase in the critical heat flux during boiling of nanofluids is associated with the formation of a layer of deposition of nanoparticles on the surface, which contributes to a change in the microcharacteristics of the heat transfer of the surface. Mathematical model and results of calculation of film boiling characteristics of nanofluid on vertical heated wall are presented. It is shown that the greatest influence on the processes of heat and mass transfer during film boiling of the nanofluid is exerted by wall overheating, the ratio of temperature and Brownian diffusion and the concentration of nanoparticles in the liquid. The mathematical model does not take into account the effect changing structure of the heated surface on heat transfer processes but it allows to evaluate the effect of various thermophysical parameters on intensity of deposition of nanoparticles on heated wall. The obtained results allow to evaluate the effect of nanofluid physical properties on heat and mass transfer at cooling of high-temperature surfaces. The using nanofluids as cooling liquids for heat transfer equipment in the regime of supercritical heat transfer promotes an increase in heat transfer and accelerates the cooling process of high-temperature surfaces. Because of low thermal conductivity of vapor in comparison with the thermal conductivity of the liquid, an increase in the concentration of nanoparticles in the vapor contributes to greater growth in heat transfer in the case of supercritical heat transfer.

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The Effect of Inclined Vertical Slats on the Free Convective Heat Transfer Rate From an Isothermal Heated Vertical Surface

Heat Transfer, Volume 2 ◽

10.1115/imece2004-61382 ◽

2004 ◽

Author(s):

Patrick H. Oosthuizen ◽

Lan Sun ◽

David Naylor

Keyword(s):

Heat Transfer ◽

Convective Heat Transfer ◽

Heat Transfer Rate ◽

Convective Heat ◽

Heat Generation ◽

Transfer Rate ◽

Heated Surface ◽

Heated Plate ◽

Study Results ◽

Free Convective Heat Transfer

Free convective heat transfer from a wide heated vertical isothermal plate with adiabatic surfaces above and below the heated surface has been considered. There are a series of equally spaced vertical thin, flat surfaces (termed “slats”) near the heated surface, these surfaces being, in general, inclined to the heated surface. The slats are pivoted about their center-point and thus as their angle is changed, the distance of the tip of the slat from the plate changes. The temperature of the vertical isothermal surfaces has been assumed to be greater than the ambient temperature. Various cases have been considered to examine the effect of the geometry of the adiabatic surfaces above and below the heated plate, the effect of heat conduction in the slats and the effect of heat generation in the slats. The situation considered is an approximate model of a window with a vertical blind, the particular case where the window is hotter than the room air being considered. The heat generation that can occur in the slats is then the result of solar energy passing through the window and being absorbed by the slats. The flow has been assumed to be laminar and steady. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces. The governing equations have been written in dimensionless form and the resulting dimensionless equations have been solved using a commercial finite-element package. Because of the application that motivated the study, results have only been obtained for a Prandtl number of 0.7. The effect of the other dimensionless variables on the mean dimensionless heat transfer rate from the heated surface has been examined.

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RESEARCH ON THE EFFECT OF PROTECTING COATING ON THE FIRE RESISTANCE OF ALUMINUM ALLOY STRUCTURES

Fire Safety ◽

10.32447/20786662.34.2019.03 ◽

2019 ◽

pp. 16-20

Author(s):

S. Y. Vovk ◽

N. O. Ferents ◽

D. V. Kharyshyn

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Aluminum Alloy ◽

Fire Resistance ◽

Protective Coating ◽

Fire Protection ◽

Protective Coatings ◽

Component Composition ◽

Thermomechanical Properties ◽

Heat Transfer Process

Polyfunctional protective coatings based on filled polysiloxane compositions are technological and can be used to increase the fire resistance of metal structural materials due to high thermomechanical properties, which are determined by stable structural and phase composition. The influence of protective coatings on the basis of polysiloxane-filled oxide components on fire resistance of aluminum alloys is investigated in the work. The choice of the initial compositions for fire protection coatings was carried out with the aim of obtaining of expanded heat-insulating heatresistant layer on the surface of an aluminum alloy at temperatures of 473 K and higher. The methods of physico-chemical analysis have established that when heated more than 473 K as a result of thermo oxidative degradation of polysiloxane with the release of gaseous products, there is an expanding coating with the formation of a fire-proof porous heat-insulating layer on the surface of an aluminum alloy. The coefficient of expanding the coating is within the range of 9.8 ... 12.4. The reliability of the use of physicochemical criteria when choosing the component composition of the coating and the effectiveness of the fire protection function is estimated from the results of the test on the aluminum alloy AMG6 and on the model of its thermal conductivity. 20 Пожежна безпека, №34, 2019 A model of thermal conductivity of a protective coating is proposed, which consists of a layer that limits heat transfer through a two-layer wall. When exposed to the aluminum plate of the heat flow, it is heated to the depth of the coating, which leads to its expanding and the formation of a thermal barrier. The dynamics of temperature distribution during a fire on the protective coating of an aluminum alloy is predicted by simulating the heat transfer process in a homogeneous solid by a mathematical model. The theoretical and practical researches have established the dependence of the parameter of heating the protected aluminum alloy to the critical temperature, depending on the thickness of the coating. The presence on the surface of a protected alloy coating, based on the filled polysiloxane, changes the process of heat transfer to its surface, which increases the fire resistance of the structure by 3 ...4 times.

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Effect of Nanofluids on Boiling Heat Transfer Performance

Applied Sciences ◽

10.3390/app9142818 ◽

2019 ◽

Vol 9 (14) ◽

pp. 2818 ◽

Cited By ~ 1

Author(s):

Shouguang Yao ◽

Zecheng Teng

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Boiling Heat Transfer ◽

Heat Dissipation ◽

Heat Transfer Performance ◽

Heated Surface ◽

Transfer Performance ◽

Wall Superheat ◽

Boiling Heat Transfer Coefficient ◽

Base Liquid

At present, there are many applications of nanofluids whose research results are fruitful. Nanofluids can enhance the critical heat flux, but the effect on boiling heat transfer performance still has disagreement. Base liquids with higher viscosity improve the boiling heat transfer performance of nanofluids. When the base liquid is a multicomponent solution, the relative movement between the different solutions enhances the microscopic movement of the nanoparticles due to the different evaporation order during the boiling process, so that the boiling heat transfer performance is enhanced. Compared with the thermal conductivity of the heated surface, the deposition of the low thermal conductivity nanoparticles reduces the heat dissipation rate of the heated surface and improves the wall superheat. Then the enhancement of the boiling heat transfer coefficient should be attributed to the thermal conductivity improvement of base fluid and the bubble disturbance resulted from the nanoparticle’s microscopic motion.

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